This invention relates to an intermittent receiving apparatus for use in a digital receiver and, in particular, to an intermittent receiving apparatus for alternately carrying out receiving operation and nonreceiving operation on a received carrier signal.
An intermittent receiving apparatus of the type described is operable in an intermittent operation. That is, the intermittent receiving apparatus alternately carries out reception operation and nonreception operation on a received carrier signal having a carrier frequency. The intermittent receiving apparatus has a received carrier input terminal supplied with the received carrier signal, a reception data output terminal for outputting reception data, and a reception clock output terminal for outputting a reception clock signal having a reception clock frequency. The reception clock frequency is identical with a reproduced clock frequency which is lower than the carrier frequency.
A conventional intermittent receiving apparatus comprises a detection circuit, a clock reproduction circuit, and an oscillation circuit. Supplied to the received carrier input terminal, the received carrier signal is supplied to the detection circuit and the clock reproduction circuit. The oscillation circuit oscillates an oscillation signal having an oscillation frequency which is equal to N times as large as the reproduced clock frequency where N represents a predetermined positive integer. The positive integer N is normally set in a value between thirty-two and three hundred. The oscillation frequency is higher than the carrier frequency.
Responsive to the received carrier signal, the clock reproduction circuit reproduces a reproduced clock signal having the reproduced clock frequency with reference to the oscillation signal. The reproduced clock signal is supplied to the detection circuit. The detection circuit detects the reception data in the received carrier signal using the reproduced clock signal as a detection timing. The reception data is supplied to the reception data output terminal. The reproduced clock signal is supplied to the reception clock output terminal as the reception clock signal.
In the above-mentioned conventional intermittent receiving apparatus, the clock reproduction circuit carries out synchronization holding operation so that the oscillation circuit always oscillates the oscillation signal having the oscillation frequency which is N times the reproduced clock frequency on the nonreception operation as well as the reception operation. As a result, the conventional intermittent receiving apparatus is disadvantageous in that the higher the oscillation frequency becomes, the larger current consumption becomes.